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What Happens When Malaria Nets Stop Working? Questioning Assumptions About Mosquitoes, and Public Health Interventions

What Happens When Malaria Nets Stop Working? Questioning Assumptions About Mosquitoes, and Public Health Interventions

Picture of Barbara Feder Ostrov

Having been feasted upon by mosquitoes when I worked in swampy South Florida, I could relate to Bora Zivkovic's excellent and counterintuitive examination of what happens when mosquitos make an end run around bed nets, which have long been used to help prevent malaria in developing countries:

As we have learned many times, often the hard way, evolution tends to find a way around such tricks. A number of Anopheles species or local populations have evolved resistance to pyrethroid insecticides usually used in the nets. Yet, the mechanical protection of the net should still be effective, right?

Not so fast! A new study published in September 21 in the Journal of Infectious Diseases documents a behavioral change in a local mosquito population that effectively works around the safety protection of bed nets. What do they do that’s new? They changed the time of day when they bite!

So what does that mean for what used to be considered a tried and true public health intervention? Are bed nets obsolete? Zivkovic writes:

It is hard to predict what will be the pros and cons of those adaptations for human health, or the pros and cons of those adaptations for mosquitoes and their survival, or pros and cons of these adaptations to insects’ predators. Future research on this will be both very interesting to watch and very useful for control of malaria.

The researchers' discovery that mosquitoes will still get their dinner despite malaria nets is a great reminder that we need to constantly challenge our assumptions about public health programs, both globally and much closer to home.

If malaria nets become less effective over time, what about other venerable public health efforts like local childhood immunization registries? Lead poisoning prevention programs? Safe sex education campaigns? That's why you should always be checking audits and evaluations of health programs — no matter how "obviously" effective they might seem.

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